Filled telephone cable

ABSTRACT

In a filled telephone cable, the core is filled with a composition comprising petroleum jelly in the amount of about 80 percent by weight, polyethylene and/or polybutene-1 in the amount of about 10 percent by weight, and polyisobutylene in the amount also of about 10 percent weight.

United States Patent 1191 Zinser, et al.

, 1451 Nov. 27, 1973 FILLED TELEPHONE CABLE [75] Inventors: Frederick M. Zinser, Jr.; Joseph Connelly, both of Decatur, Ill.

[73] Assignee: Essex International, Inc., Fort Wayne, Ind.

22 Filed: Feb. 24, 1972 211 App]. No.: 228,876

[52] Us. or. 174/23 0, 174/25 0, 174/107, .,174/11o PM, 174/116 511 1111. c1. ..H0lb-7/l8,HO'lb 3/30,

[58] Field of Search 174/23 R, 23- c, 25 c, 174/27, 24, 110 PM, 113 R, 116, 107, 102 R,

[56] 7 References Cited UNITED STATES PATENTS 3,607,487 9/1971 Biskeborn 174/23 C 3,622,683 11/1971 Roberts 174/107 X 3,642,638 2/1972 Kitano et a1. 174/1 10 PM FOREIGN PATENTS OR APPLICATIONS 1,095,639 12/1967 Great Britain l74 /l 16 757,395 9/1956 Great Britain 174/25 C 767,836 2/1957 Great Britain 174/25 C 776,174 6/1957 Great Britain 174/25 C Primary Examiner-Bernard A. Gilheany Assistant Examiner-A. T. Grimley Att0rney-A. W. Molinare et a1.

[5 7] ABSTRACT In a filled telephone cable, the core is filled with a composition comprising petroleum jelly in the amount of about 80 percent by weight, polyethylene and/or polybutene-l in the amount of about 10 percent by weight, and polyisobutylene in the amount also of about 10 percent weight.

6 Claims, 2 Drawing Figures mjr-rnrnzo x'o-mcozon g'mmn umm ms v 3,775,548-

PRELIMINARY TW'ST FLOODING TANKS 30 3/ a2 FILLER. 40 v V FLOODING 42 r TANK 33 K v '44 CORE. METALLIC INSULATOR' ,WRAP SHIELD SHEATH O l0, 7 FORMING {REEL FILLED TELEPHONE CABLE BACKGROUND "AND SUMMARY OF THE INVENTION resultin a substantial reduction in the performance of the cable,'if not complete destruction for its intended 1 purpose.

In order to reduce the likelihoodof damage to suc underground cables, for example underground telephone cables, various fillers have been employed in'the past to prevent exposure of the cable conductors to water. Suchfilled cables generally take the form of a core in which the multiple conductors of v the telephone 'cable are embedded in a soft resilient filler material during'manufacture the purpose of which is to fill all the voids within the cable. This core is then wrapped with a suitable dielectric tape, is covered with a metallic sheath and is coated with the external insulative sheath of the'cable. One such filler composition which has been employed in'the past comprises a mixture of 85-95 percent petroleum jelly and 5-15 percent polyethylene. During the "manufacture of the'cable, the

filler material is heated -'to a temperature at which it is a flowable heavy viscous liquid which is coated upon the multiple conductors so as to fill the voids between the conductors. Upon cooling to ambient temperature, the filler composition assumes a non-flowable, pliable, 't'acky form and is closely contained in the cable core by the external sheathing of the cable.

It hasbe'en found that prior'petroleum jelly polyethylene mixtures tend to dry and crack after injection into the cable. As such, whenthe cable is bent during installation, voids may occur in the cable core which might allow moisture to penetrate the conductor insulation. It is believedthat'such drying and cracking is due to the absorption of the light ends'of the petroleum jelly into the polyvinyl chloride, polyethylene or polypropylene cable insulation and which causes this insui tion for filled cables which substantially reduces the tendency of such" cables to dry out and crack and thereby substantially increasesthe life and operating performance of these cables. Moreover, the composition of the present invention is not appreciably more expensivethanthe prior filling compositions and may be readily applied during manufacture of the cable by well known processes which were previously employed in the application of the prior filling compositions.

In a principal aspectof the present invention, a composition for filling filled conductive cables comprises a mixture of about 80 weight percent petroleum jelly,

about 10 weight percent of either polyethylene and/or polybutene-l and about 10 weight percent of polyisobutylene.

In another principal aspect of the present invention, a filled communication cable comprises a core having a plurality of insulated conductors therein and a filler composition filling the spaces between and surrounding the conductors. The filler composition comprises a mixture of about weight percent of petroleum jelly, about 10 weight percent polyethylene and/or polybutene-l and about 10 weight percent polyisobutylene and an exterior sheath covers the core.

These and other objects, features arid advantages of the present invention will become evident upon consideration'of the following detailed description.

. BRIEF DESCRIPTION OF TI-IEDRAWING In the course of this detailed description, the drawings will be referred to in which:

FIG. 1 is a cross-sectioned view of a filled telephone cable construction incorporating the principles of the present invention; and

FIG. 2 is a schematic presentation in which a preferred sequence of construction steps are shown for making a filled telephone cable incorporating the principles of the present invention.

l DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a filled telephone cable constructed in accordance with the principles of the present invention is shown which comprises a core, generally 10, which is surrounded by an external sheath, generally 12. The core 10 includes a plurality of spaced conductor pairs 14 which are twisted together. Each of the conductors 16 in the given pair 14 comprises a suitable conductor wire 18, such as an aluminum or copper wire, which is surrounded with an insulative coating 20, such as polyethylene, polypropylene or polyvinyl chloride. Each of the conductor pairs are spaced from each other and the spaces between the pairs are filled with the filler composition 22 of the present invention as shown in FIG. 1.

The filler composition of the present invention comprises a mixture of petroleum jelly, polyethylene, and polyisobutylene, the latter of which is a tackifying agent. The petroleum jelly is present in the filler in the amount of 80 percent by weight, the polyethylene in the amount of 10 percent by weight, and the polyisobutylene in the amount of 10 percent by weight. It has been found that a mixture of these materials in the above mentioned amounts provides a filler composition which exhibits suitable melting temperatures which are important in the application of the filler composition to the conductors, as will be explained in further detail later. Such composition has also been found to be sufficiently tacky, but not overly tacky, and is capable of relatively easy mixing. Finally and, most importantly, this composition substantially reduces the tendency of the filled cable to dry and crack.

The percentages of the filler mixture components are important in achieving a filler composition which is" both readily workable and which reduces drying and cracking of the filler in the cable. Where the percentage of petroleum jelly is reduced to 78 percent and the percentage of polyisobutylene is increased to 17 percent, the resulting mixture becomes too tacky and the melt temperature of the filler material is increased by an unacceptable amount. Conversely, a mixture of 86 percent petroleum jelly 10 percent polyethylene lativelayer 28, such as polypropylene or 4 percent polyisobutylene was found to be not sufficiently tacky. When the amount of polyethylene is reduced to 2 percent, the melting temperature of the mixture is not sufficiently high to prevent loss of the filler from the end of the cable at temperatures which might be experienced in installations in hot geographic regions, e.g. 160F.

Although, polyethylene is preferred, it is contemplated that poIybutene-l may also be substituted in whole or in part for the polyethylene. Where polyethylene is employed, the low density form is preferred and polyethylenes having average molecular weights in the range of from 3,000 to 400,000 have been found to be suitable. A suitable polyisobutylene is Vistanex, available from Enjay Chemical Co.

Referring again to FIG. 1, the sheath 12 surrounds the core and comprises a wrapped layer of a suitable dielectric tape 24, such as a polyester type. This tape layer is also preferably impregnated with the tiller mixture. Surrounding the tape layer. 24 of the cable, is a suitable metallic sheath 26, such as aluminum and, finally, the cable is covered with an exterior flexible insupolyvinyl chloride. l

Although it is believed that the foregoing description of the filled cable isample for a full understanding of the principles of the invention, a brief description of a suitable method for making such cable follows.

Referring to FIG. 2, the already insulated individual conductors 16 are drawn from individual reels 30 and a pair of these conductors are twisted together at 31 to form pairs 14. These pairs 14 are then passed through filler flooding tanks 32 in which each of the respective pairs is saturated and coated with the filler mixture earlier described. The heated filler is introduced to the flooding tanks 32 at a temperature of approximately 210 F at which temperature, the filler mixture takes the form of a heavy, viscous liquid and readily flows between and coats the conductor pairs. Since the conductor pairs 16 enter tanks 32 at substantially ambient temperature, the temperature of the tiller mixture which is coated upon the pairs will be reduced such that the filler on the pairs will become tacky and grease-like and will therefore adhere to the pairs a they leave tanks 32.

A plurality of these coated pairs 14 are then brought into proximity to each other at 34 and enter a second flooding tank 36 to which additional filler mixture has also been introduced in the liquid state. In this flooding tank 36, the filler will now flow between the conductor pairs 14 to fill the spaces between the pairs and will surround the entire conductor bundle as shown in FIG. 1. Again contact with the proximate conductor pairs will result in a reduction in the temperature of the filler mixture, causing it to become greasy and tacky in consistency as previously described.

The core 10 which has now been formed will then pass to a core wrap station 38 where the core is wrapped with the polyester tape 24. The wrapped core 10' then proceeds to a metallic sheath application station 40 in which the metallic sheath 26 is applied. Finally, this sheathed bundle 10" passes to an insulator sheath forming station 42 where the external insulative sheath is applied and cured. From this station, the filled final cable product may be stored on reels 44.

It will be understood that the embodiment of the present invention which has been described is merely illustrative of one of the applications of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

What is claimed is 1. A composition for filling communication cables, said composition comprising a mixture of:

petroleum jelly in the amount of about weight percent of said composition,

a polymer selected from the group consisting of polyethylene, polybutene-l and mixtures thereof in the amount of about 10 weight percent of said composition, and

polyisobutylene in the amount of about 10 weight percent of said composition.

2. The composition of claim 1 wherein said polyethylene is low density polyethylene.

3. A filled communication cable comprising,

a core including a plurality of insulated conductors and a filler composition filling the spaces between and surrounding said conductors, said composition comprising a mixture of: petroleum jelly in the amount of about 80 weight percent of said composition,

a polymer selected from the group consisting of polyethylene, polybutene-l and mixtures thereof in the amount of about 10 weight percent of said composition, and

polyisobutylene in the amount of about 10 weight percent of said composition, and

an exterior sheath covering said core.

4. The cable of claim 3 wherein said polyethylene is low density polyethylene.

5. The cable of claim 3 wherein said exterior sheath includes a tape wrapped about said core, said tape being impregnated with said filler composition.

6. The cable of claim 5 wherein said exterior sheath also includes an insulative coating surrounding said tape. 

2. The composition of claim 1 wherein said polyethylene is low density pOlyethylene.
 3. A filled communication cable comprising, a core including a plurality of insulated conductors and a filler composition filling the spaces between and surrounding said conductors, said composition comprising a mixture of: petroleum jelly in the amount of about 80 weight percent of said composition, a polymer selected from the group consisting of polyethylene, polybutene-1 and mixtures thereof in the amount of about 10 weight percent of said composition, and polyisobutylene in the amount of about 10 weight percent of said composition, and an exterior sheath covering said core.
 4. The cable of claim 3 wherein said polyethylene is low density polyethylene.
 5. The cable of claim 3 wherein said exterior sheath includes a tape wrapped about said core, said tape being impregnated with said filler composition.
 6. The cable of claim 5 wherein said exterior sheath also includes an insulative coating surrounding said tape. 